Composite items are generally constructed from layers of material that are laminated together. These layers are often referred to as partial or full plies. For structures exceeding the available material width, each layer is typically made up of a series of strips or courses of material placed edge to edge next to each other or are overlapped to some extent. Each ply may be in the form of woven fibers in a fabric, unidirectional fiber material, metal foils, adhesive films or a variety of other conformations. Unidirectional fiber material is often termed, “tape.” The fibers may be made from any of a multitude of natural and/or “man-made” materials such as fiberglass, graphite, Kevlar®, and the like.
The courses are generally laid upon the form or tool in a specific pattern. Deviations from this pattern may result in unacceptable wrinkles, twist, gaps and/or overlap of the courses. Other errors that may occur during ply placement include foreign objects, such as, bits of backing material or debris (“blobs”) becoming stuck to the surface of the tool or course. Blobs generally include bits of resin and stray fibers pulled from the tape that may ball up into “fuzz balls” or fiber wads.
In these and other instances, if the error is not identified and corrected prior to placement of the next ply, material properties of the completed composite item may be adversely affected. Conventionally, technicians have been employed to inspect the courses. This typically involves stopping course placement while the inspection occurs to insure thorough inspection and minimize risk to the technicians. Accordingly, inspection greatly increases the fabrication time and expense of the composite item. In an attempt to assist the inspection technicians, conventional machine vision systems have been utilized in the inspection process. However, these conventional machine vision systems are not capable of identifying all of the various types of anomalies. Nor are they capable of inspecting at the laydown rates currently achievable with multi-head tape lamination machines.
Accordingly, it is desirable to provide a method and apparatus capable of overcoming the disadvantages described herein at least to some extent.